"The music for the Mass is found in three books: the Kyriale (for the people), the Graduale (for the schola), and the Missale (for the priest)."-via
I'll still probably have some trouble keeping this straight, but previous to this I had seen all three books mentioned but did not have any idea that they belonged to specific entities in the Mass. In my mind they were just a jumble of names of music books that had something to do with the Mass.
And when you look at the page linked above you'll see that this WILT could actually be WILTS #1 thru 10. I foresee the New Liturgical Movement blog providing many WILTs in the future. Thanks NLM!